Gel-like Heat-transfer Sheet for Focus Ring Cooling
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Solution Overview
Problem
In substrate processing apparatuses, the formation of minute gaps between the focus ring and the electrostatic chuck leads to inefficient heat transfer, causing the focus ring to overheat, which results in non-uniform etching and reduced lifespan due to inadequate adhesion and the formation of a vacuum heat insulating layer during plasma etching.
Innovation Solution
A heat-transfer structure using a gel-like material with a hardness-to-thermal-conductivity ratio less than 20 is interposed between the consumable component (focus ring) and the cooling component, effectively filling gaps and improving heat transfer, keeping the focus ring at 225°C or less during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat-transfer medium made of conductive silicon rubber is interposed between the focus ring and the electrostatic chuck, then the degree of adhesion is improved and heat transference is enhanced, but the focus ring temperature cannot be reduced to 225°C or less due to low fluidity of the material
Solution Approach 1:
The patent changes the physical state parameter of the heat-transfer material from solid (conductive silicon rubber) to liquid (heat-transfer liquid), enabling the material to flow and fill minute gaps effectively. This parameter change allows the liquid to penetrate and adhere to microscopic surface irregularities, creating optimal thermal contact that reduces the focus ring temperature to 225°C or less while maintaining etching uniformity
Solution Approach 2:
The heat-transfer liquid acts as an intermediary substance between the focus ring and the electrostatic chuck, facilitating efficient heat transfer. The liquid medium fills the interface gaps and provides a continuous thermal conduction path, solving the adhesion and heat transfer problems that prevent effective cooling of the focus ring
2Duration of action of stationary object
If the focus ring temperature is high, then polymer film formation is reduced and plasma exposure increases focus ring wear, but heat transfer efficiency deteriorates due to vacuum heat insulating layer formation
Solution Approach 1:
The heat-transfer liquid serves as a mediator that eliminates the vacuum heat insulating layer by filling the microscopic gaps at the interface between the focus ring and electrostatic chuck. This liquid intermediary maintains continuous thermal contact despite the vacuum environment, enabling efficient heat removal while allowing the focus ring to operate at lower temperatures that promote polymer film formation and protect against plasma wear
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances heat transfer between the focus ring and the electrostatic chuck, maintaining the focus ring at a stable temperature, improving etching uniformity and extending its lifespan while preventing heat accumulation and wear.
Implementation Method 1
a heat-transfer member interposed between the consumable component and the cooling component and made of a gel-like material
Implementation Method 2
it has high fluidity, it can fill minute gaps in a boundary between the focus ring and the electrostatic chuck
Implementation Method 3
helium (He) gas with high heat transference is caused to flow toward the back side of the wafer from the upper surface of the electrostatic chuck so as to improve heat transference between the electrostatic chuck and the wafer
Implementation Method 4
since the interior of the chamber is evacuated during etching, these minute gaps form a vacuum heat insulating layer, causing deterioration of heat transference
Data Source
AI summary
A heat-transfer structure which can keep a consumable component at a temperature of 225° C. or less during etching of a substrate. The heat-transfer structure is disposed in a chamber where plasma processing is performed on a wafer as the substrate under a reduced pressure. The heat-transfer structure is comprised of a focus ring having an exposed surface exposed to plasma, a susceptor and an electrostatic chuck that cool the consumable component, and a heat-transfer sheet interposed between the focus ring and the electrostatic chuck and made of a gel-like material. The ratio of hardness of the heat-transfer sheet expressed in Asker C to thermal conductivity of the heat-transfer sheet expressed in W/m·K is less than 20.